1. Field of the Invention
This invention relates generally to display screens and, more particularly, to a method and apparatus for controlling the illumination of a display screen.
2. Description of the Related Art
This section is intended to introduce the reader to various aspects of art which may be related to various aspects of the present invention which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Liquid crystal displays, which are commonly known as LCD displays, have been used for a number of years in a wide variety of applications. LCD displays are probably most commonly used for small digital readouts, such as the digital displays found in watches and calculators. The area of such LCD displays is typically no larger than one square inch. As most people who own a watch or calculator having an LCD display are aware, LCD displays must be illuminated for viewing in dim lighting. Accordingly, most devices having relatively small LCD displays include a light source that effectively illuminates the display so that the user of the device can read the display in dimly lit environments.
LCD displays have become increasingly larger in size and, thus, are being used in applications much more complex than providing a simple digital readout. For example, LCD displays are currently a popular choice for desktop computers, portable computers, personal information organizers, point-of-sale (POS) terminals, interactive kiosks, and the like. The area of these relatively large displays is typically greater than five square inches, and these displays may be larger than 100 square inches. These displays are typically illuminated using one or more lamps in an edge lit backlight design.
For edge lit backlights, elongated lamps have been developed in conjunction with diffusion screens. In one typical arrangement, usually used for indoor higher ambient light applications such as factory automation, a first elongated lamp is placed at the top of an LCD display and a second elongated lamp is placed at the bottom of the LCD display. A diffusion screen is placed behind the LCD display between the first and second lamps. This type of diffusion screen is a single sheet of plastic that has reflectors formed in it. These reflectors get progressively larger toward the center of the diffusion screen. To illuminate the LCD display, both lamps are illuminated and the light from each lamp is diffused by the diffusion screen to provide a relatively consistent brightness level over the entire area of the LCD display.
In another typical arrangement, usually used for lower powered devices, a single elongated lamp is placed at the top of an LCD display and a diffusion screen is placed behind the LCD display below the lamp. This type of diffusion screen is also a single sheet of plastic that has reflectors formed in it. However, unlike the previously discussed diffusion screen, these reflectors get progressively larger toward the bottom of the diffusion screen. To illuminate the LCD display, the lamp is illuminated and the light from the lamp is diffused by the diffusion screen to provide a relatively consistent brightness level over the entire area of the LCD display.
For increased brightness, multiple lamps can be used in place of the above single lamps. For displays being used in high ambient light conditions, it is desirable to have a sufficient brightness and uniformity to allow a user to view text and graphics effortlessly. The edge lit backlight typically does not provide an adequate level of image brightness for sunlight readable applications.
To address this problem, a direct backlight using multiple lamps replaces the edge lit backlight. This design can provide over 5 times the display image brightness of an edge lit LCD. These types of displays are not very efficient at transferring light from the bulbs, resulting in a significant loss of light in the transfer from the lamps through the diffusion screen to the LCD display (e.g., a loss of ⅔ of the luminous output from the lamps). For portable and battery powered devices, where battery consumption, size, cost, and efficiency are all important design considerations, this relatively low transfer efficiency is a significant problem.
These types of LCD displays also suffer from various other image quality concerns, such as non-uniformity, glare, reflections, lack of clarity, and a variety of coloration problems such as color separation (e.g., specking artifacts, or rainbow effect that moves with eye movement). Many of these concerns, including brightness and image quality, are more apparent in an outdoor atmosphere (e.g., sunlight, rain, hot and cold temperatures, pollution, etc.), where many LCD displays are now being used.
Accordingly, the present invention may address one or more of the matters set forth above.
Certain aspects commensurate in scope with the originally claimed invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
In accordance with one aspect of the present invention, there is provided a reflector panel adapted for uniformly lighting a display having a plurality of lamps. The reflector panel may include a reflective surface having a plurality of curved sections, the reflective surface being configured to reflect light away from the plurality of lamps and into a plurality of intermediate areas between the plurality of lamps.
In accordance with another aspect of the present invention, there is provided a system for uniformly lighting a display. The system may include a plurality of elongated lamps configured to be disposed behind the display, and a reflector panel configured to be disposed behind the plurality of elongated lamps at a desired offset distance from the display. The reflector panel includes a reflective surface having a plurality of curved sections configured to reflect light substantially around the elongated lamps and into a plurality of intermediate areas between the plurality of elongated lamps. The plurality of curved sections may form a plurality of curved depressions each of which are disposed at least partially behind one of the plurality of elongated lamps.
In accordance with another aspect of the present invention, there is provided a display system. The display system may include a display screen, a diffusion screen disposed behind the display screen, a plurality of elongated lamps disposed behind the diffusion screen and configured to emit light, and a reflector panel disposed behind the plurality of elongated lamps at a desired offset distance from the display screen. The reflector panel includes a reflective surface having a plurality of curved sections configured to reflect light substantially around the elongated lamps and into a plurality of intermediate areas between the plurality of elongated lamps. The plurality of curved sections may form a plurality of curved depressions each of which are disposed at least partially behind one of the plurality of elongated lamps.
In accordance with another aspect of the present invention, there is provided a method of illuminating a display screen. The method may include the act of disposing a reflector panel behind a plurality of elongated lamps positioned adjacent the display screen for illuminating the display screen, wherein the reflector panel has a reflective surface comprising a plurality of elongated curved portions. The plurality of elongated curved portions also may be positioned at a desired position relative to the plurality of elongated lamps such that the reflective surface can reflect light substantially around the elongated lamps and into a plurality of intermediate areas between the plurality of elongated lamps. Moreover, the reflector panel may be positioned at a desired offset distance from the display screen to facilitate substantially uniform illumination of the display screen.
In accordance with another aspect of the present invention, there is provided a method of forming a light reflector assembly for a display. The method may include the acts of forming a reflector panel with a plurality of curved depressions, and forming a reflective surface on the reflector panel for distributing light substantially uniformly toward the display screen. Each of the curved depression are configured to be positioned behind one of the plurality of lamps, which are positioned adjacent a display screen. The reflective surface includes a curved portion disposed in the plurality of curved depressions, providing substantially specular reflection, and an intermediate portion disposed between the plurality of curved depressions, providing substantially diffuse reflection.